| Paper | Title | Page |
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| TUAX02 | Coherent Instabilities at the Fermilab Booster | 69 |
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Fermilab booster is a fast cycling synchrotron operating on 15 Hz. To exclude problem of eddy currents excited in the vacuum chamber by fast changing magnetic field Booster does not have a conventional vacuum chamber. Instead, the vacuum chamber is formed by poles of the laminated combined function magnets. The exposed magnet laminations result in large transverse and longitudinal impedances affecting both the transverse and longitudinal stability of the beam. Presently, the transverse instability is suppressed by large chromaticity negatively affecting the dynamic aperture and the beam lifetime. Earlier attempts to stabilize the instability by transverse feedback system were unsuccessful. Recently we performed experimental studies to find out the reason. We observed that at reduced chromaticity at injection the most unstable mode is the multibunch high order head-tail mode with growth time of about 12 turns. It develops at synchro-betatron tune with very small fractional part where the transverse impedance is at a maximum. Analytical calculations and numerical simulations verify the observations and allowed us to compute the value of transverse impedance. Another persistent probl
Work supported by the Universities Research Assos., Inc., under contract DE-AC02-76CH03000 with the U. S. Dept. of Energy. |